class Solution:
    def isInterleave(self, s1: str, s2: str, s3: str) -> bool:
        m, n, mn = len(s1), len(s2), len(s3)
        if m + n != mn:
            return False
        dp = [[False] * (n + 1) for _ in range(m + 1)]
        dp[0][0] = True
        for i in range(1, n + 1):
            dp[0][i] = dp[0][i - 1] and s2[i - 1] == s3[i - 1]
        for i in range(1, m + 1):
            dp[i][0] = dp[i - 1][0] and s1[i - 1] == s3[i - 1]

        for i in range(1, m + 1):
            for j in range(1, n + 1):
                dp[i][j] = (dp[i][j - 1] and s2[j - 1] == s3[i + j - 1]) or \
                           (dp[i - 1][j] and s1[i - 1] == s3[i + j - 1])
        return dp[-1][-1]


if __name__ == '__main__':
    s = Solution()
    print(s.isInterleave('aabcc', 'dbbca', 'aadbbcbcac'))
    print(s.isInterleave('aabcc', 'dbbca', 'aadbbbaccc'))
    print(s.isInterleave('a', '', 'a'))
